WO2021012680A1 - Imaging lens system - Google Patents

Abstract

An imaging lens system (100), comprising in sequence from the measured object end to the image end: a panel of glass (G1); a first lens (L1) which has a negative focal power, the object side surface thereof (S3) being a convex surface and the image side surface thereof (S4) being a concave surface; a second lens (L2) which has a positive focal power, the object side surface thereof (S5) being a convex surface and the image side surface thereof (S6) being a concave surface; a stop (ST); a third lens (L3) which has a positive focal power, the image side surface thereof (S8) being a convex surface. An effective focal length f and the entry pupil diameter (EPD) of the imaging lens system (100) satisfy: f/EPD≤1.6; three lenses are present in the imaging lens system (100); the imaging lens system (100) satisfies the conditional formula: 0<BFL/IH<0.2, wherein BFL represents the distance between the highest point of the third lens (L3) and the image surface, and IH represents the maximum image height of the imaging lens system (100). The total optical length of the imaging lens system (100) is made shorter by means of reasonably matching and defining each lens and the stop, which helps to miniaturize the lenses.

Description

Imaging lens system

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office with the application number 2019106642917 and the invention title "Imaging Lens System" on July 23, 2019, the entire content of which is incorporated into this application by reference.

Technical field

The invention relates to the technical field of optical lenses, in particular to an imaging lens system.

Background technique

Fingerprint imaging recognition technology is a technology that collects a fingerprint image of a human body through a fingerprint recognition device, and then compares it with the existing fingerprint image information in the system to realize identity recognition. Due to its ease of use and the uniqueness of human fingerprints, fingerprint recognition technology has been widely used in various fields, such as security inspections such as public security and customs, building access control systems, and consumer products such as personal computers and mobile phones.

The imaging lens system is often used as a part of the fingerprint recognition device under the screen. It collects fingerprint information (the end points and bifurcation points of the fingerprint texture seen by the human eye) through the imaging principle, and processes the algorithm to sharpen the collected peak and valley information. Compare with fingerprint database information to achieve the effect of fingerprint recognition. However, the existing imaging lens system still has the problem of long optical total length, which is not conducive to the development of miniaturization of the lens.

Summary of the invention

To this end, the purpose of the present invention is to provide an imaging lens system to solve the problem of long optical total length.

An imaging lens system, from the measured object end to the image side end, includes:

plate glass;

For the first lens with negative refractive power, the object side surface is convex, and the image side surface is concave;

For the second lens with positive refractive power, its object-side surface is convex, and its image-side surface is concave;

Aperture

The third lens with positive refractive power has a convex surface on the image side;

The effective focal length f of the imaging lens system and the entrance pupil diameter EPD satisfy: f/EPD≤1.6;

The number of lenses in the imaging lens system is three;

The imaging lens system satisfies the conditional formula:

0＜BFL/IH＜0.2;

Wherein, BFL represents the distance from the highest point of the third lens to the image plane, and IH represents the maximum image height of the imaging lens system;

The imaging lens system also satisfies the conditional formula:

-0.73＜(CT3-CT1)/(ET1-ET3)＜-0.45;

Wherein, CT3 represents the central thickness of the third lens, CT1 represents the central thickness of the first lens, ET3 represents the edge thickness of the third lens, and ET1 represents the edge thickness of the first lens.

The imaging lens system provided by the present invention makes the total optical length of the imaging lens system shorter by reasonably matching and limiting each lens and the diaphragm, which is beneficial to the miniaturization of the lens.

In addition, the imaging lens system satisfies the conditional formula:

0.17<(SAG12-SAG11)/CT1<0.43;

Wherein, SAG12 represents the sagittal height of the image side surface of the first lens, SAG11 represents the sagittal height of the object side surface of the first lens, and CT1 represents the center thickness of the first lens.

Further, the imaging lens system satisfies the conditional formula:

1.36＜f3/f＜1.56;

Wherein, f3 represents the effective focal length of the third lens, and f represents the effective focal length of the imaging lens system.

Further, the imaging lens system satisfies the conditional formula:

(ND3-ND2)/(VD3-VD2)<0;

Wherein, ND3 represents the refractive index of the third lens, ND2 represents the refractive index of the second lens, VD3 represents the Abbe number of the third lens, and VD2 represents the Abbe number of the second lens.

Further, the imaging lens system satisfies the conditional formula:

0.3<f3/f2<0.4;

Wherein, f3 represents the effective focal length of the third lens, and f2 represents the effective focal length of the second lens.

Further, the imaging lens system satisfies the conditional formula:

-2＜(R32-R31)/(R32+R31)＜-1.3;

Wherein, R32 represents the radius of curvature of the image side surface of the third lens, and R31 represents the radius of curvature of the object side surface of the third lens.

Further, the surface shape of the aspheric surface of the imaging lens system satisfies the following conditional formula:

Among them, z represents the distance of the surface from the surface vertex in the optical axis direction, c represents the curvature of the surface vertex, k represents the quadric surface coefficient, h represents the distance from the optical axis to the surface, B, C, D, E, F, G, H represents the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order surface coefficients respectively.

Description of the drawings

The above and/or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, in which:

1 is a schematic diagram of the structure of the imaging lens system in the first embodiment of the present invention;

2 is a graph of the spherical aberration of the imaging lens system on the axis in the first embodiment of the present invention;

3 is a graph of lateral chromatic aberration of the imaging lens system in the first embodiment of the present invention;

4a is a field curvature curve diagram of the imaging lens system in the first embodiment of the present invention;

4b is a distortion curve diagram of the imaging lens system in the first embodiment of the present invention;

5 is a schematic diagram of the structure of the imaging lens system in the second embodiment of the present invention;

6 is a graph of the spherical aberration curve of the imaging lens system in the second embodiment of the present invention;

7 is a graph of lateral chromatic aberration of the imaging lens system in the second embodiment of the present invention;

Fig. 8a is a field curvature curve diagram of the imaging lens system in the second embodiment of the present invention;

8b is a distortion curve diagram of the imaging lens system in the second embodiment of the present invention;

9 is a schematic diagram of the structure of the imaging lens system in the third embodiment of the present invention;

10 is a graph of the spherical aberration curve of the imaging lens system in the third embodiment of the present invention;

11 is a graph of lateral chromatic aberration of the imaging lens system in the third embodiment of the present invention;

Fig. 12a is a field curvature curve diagram of an imaging lens system in a third embodiment of the present invention;

Fig. 12b is a distortion curve diagram of the imaging lens system in the third embodiment of the present invention;

13 is a schematic diagram of the structure of the imaging lens system in the fourth embodiment of the present invention;

14 is a graph of the spherical aberration curve of the imaging lens system in the fourth embodiment of the present invention;

15 is a graph of lateral chromatic aberration of the imaging lens system in the fourth embodiment of the present invention;

Fig. 16a is a field curvature curve diagram of an imaging lens system in a fourth embodiment of the present invention;

Fig. 16b is a distortion curve diagram of the imaging lens system in the fourth embodiment of the present invention.

Detailed ways

In order to make the objectives, features and advantages of the present invention more comprehensible, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Several embodiments of the invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present invention. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The term "and/or" as used herein includes any and all combinations of one or more related listed items.

The present invention provides an imaging lens system, which sequentially includes from the object end to the image side end:

plate glass;

For the first lens with negative refractive power, the object side surface is convex, and the image side surface is concave;

The second lens has a convex surface on the object side and a concave surface on the image side;

Aperture

The third lens with positive refractive power has a convex surface on the image side;

The effective focal length f of the imaging lens system and the entrance pupil diameter EPD satisfy: f/EPD≤1.6;

In some embodiments, the imaging lens system satisfies the conditional formula:

0.17<(SAG12-SAG11)/CT1<0.43; (1)

Wherein, SAG12 represents the sagittal height of the image side surface of the first lens, SAG11 represents the sagittal height of the object side surface of the first lens, and CT1 represents the center thickness of the first lens.

The first lens bears a large negative optical power, diverges the light of the large field of view, and enters the optical system smoothly and without too much light turning. This can ensure that the large field of view does not require an excessively large advanced Aberrations to correct.

In some embodiments, the imaging lens system satisfies the conditional formula:

1.36＜f3/f＜1.56; (2)

Wherein, f3 represents the effective focal length of the third lens, and f represents the effective focal length of the imaging lens system.

Satisfying the above conditional formula (2) is beneficial to reduce the spherical aberration and shorten the length of the lens. The spherical aberration refers to the blur of image quality caused by different apertures on the axis and the focal position of the optical axis.

In some embodiments, the imaging lens system satisfies the conditional formula:

(ND3-ND2)/(VD3-VD2)＜0; (3)

Wherein, ND3 represents the refractive index of the third lens, ND2 represents the refractive index of the second lens, VD3 represents the Abbe number of the third lens, and VD2 represents the Abbe number of the second lens.

Satisfying the above conditional formula (3) can effectively shorten the total optical length of the lens and promote the miniaturization of the lens.

In some embodiments, the imaging lens system satisfies the conditional formula:

0.3＜f3/f2＜0.4; (4)

Wherein, f3 represents the effective focal length of the third lens, and f2 represents the effective focal length of the second lens.

Satisfying the above conditional formula (4), the optical power of the system can be allocated reasonably, the difficulty of aberration correction can be reduced, and the system can achieve better quality.

In some embodiments, the imaging lens system satisfies the conditional formula:

-2＜(R32-R31)/(R32+R31)＜-1.3; (5)

Wherein, R32 represents the radius of curvature of the image side surface of the third lens, and R31 represents the radius of curvature of the object side surface of the third lens.

Satisfying the above conditional formula (5), the system can obtain a larger NA value (numerical aperture) and improve the resolution of the system.

In some embodiments, the imaging lens system satisfies the conditional formula:

-0.73＜(CT3-CT1)/(ET1-ET3)＜-0.45; (6)

Wherein, CT3 represents the central thickness of the third lens, CT1 represents the central thickness of the first lens, ET3 represents the edge thickness of the third lens, and ET1 represents the edge thickness of the first lens.

Satisfying the above conditional formula (6) is beneficial to the correction of curvature of field and astigmatic aberration of the system.

In some embodiments, the imaging lens system satisfies the conditional formula:

0＜BFL/IH＜0.2; (7)

Wherein, BFL represents the distance from the highest point of the third lens to the image plane, and IH represents the maximum image height of the imaging lens system.

Satisfying the above conditional formula (7) can effectively shorten the system length and realize miniaturization.

In some embodiments, the surface shape of the aspheric surface of the imaging lens system satisfies the following conditional formula:

Among them, z represents the distance of the surface from the surface vertex in the optical axis direction, c represents the curvature of the surface vertex, k represents the quadric surface coefficient, h represents the distance from the optical axis to the surface, B, C, D, E, F, G, H represents the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order surface coefficients respectively.

In the above imaging lens system, the first lens has negative refractive power, the object side surface is convex, the image side surface is concave, the object side surface of the second lens is convex, the image side surface is concave, and the third lens has positive light The image side surface is convex, and the diaphragm is located between the second lens and the third lens. The effective focal length f of the imaging lens system and the entrance pupil diameter EPD satisfy: f/EPD≤1.6. The reasonable collocation and limitation of the stop makes the total optical length of the imaging lens system shorter, which is beneficial to the miniaturization of the lens.

The present invention will be further described in several embodiments below. In each of the following embodiments, the thickness and radius of curvature of each lens in the imaging lens system are different. For specific differences, please refer to the parameter table in each embodiment. The following examples are only preferred implementations of the present invention, but the implementations of the present invention are not limited only by the following examples, and any other changes, substitutions, combinations or simplifications that do not depart from the innovations of the present invention, All should be regarded as equivalent replacement methods, and they are all included in the protection scope of the present invention.

Example 1:

Referring to FIG. 1, the imaging lens system 100 provided by the first embodiment of the present invention includes in turn from the object end to the image side end:

Flat glass G1, which has an object side surface S1 and an image side surface S2;

The first lens L1 with negative refractive power has an object side surface S3 and an image side surface S4, the object side surface S3 is a convex surface, and the image side surface S4 is a concave surface;

The second lens L2 with positive refractive power has an object side surface S5 and an image side surface S6, the object side surface S5 is a convex surface, and the image side surface S6 is a concave surface;

Stop ST;

The third lens L3 with positive refractive power has an object side surface S7 and an image side surface S8, and the image side surface S8 is convex.

The imaging lens system 100 provided in the first embodiment of the present invention satisfies the conditions of Table 1-1 and Table 1-2. The focal length f of the imaging lens system 100 is 0.39 mm, the total optical length is 5.0 mm, the aperture number F# is 1.6, and the field angle 2θ is 132°. The six even-order aspheric surfaces of the three lenses of this embodiment do not use the twelfth, fourteenth, and sixteenth order aspheric coefficients.

Table 1-1

Table 1-2

In the above table, A ₄ , A ₆ , A ₈ , and A ₁₀ refer to the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, respectively.

In this embodiment, the on-axis point spherical aberration, lateral chromatic aberration, curvature of field, and distortion are shown in Figs. 2, 3, 4a and 4b, respectively. Since the smaller the data range of the image point, the better the performance of the lens. It can be seen from Figure 2 to Figure 4b that the on-axis point spherical aberration, lateral chromatic aberration, field curvature and distortion are all well corrected.

Example 2

Referring to FIG. 5, the imaging lens system 200 provided by the second embodiment of the present invention includes in turn from the object end to the image side end:

Flat glass G1, which has an object side surface S1 and an image side surface S2;

The first lens L1 with negative refractive power has an object side surface S3 and an image side surface S4, the object side surface S3 is a convex surface, and the image side surface S4 is a concave surface;

The second lens L2 has an object side surface S5 and an image side surface S6, the object side surface S5 is a convex surface, and the image side surface S6 is a concave surface;

Stop ST;

The third lens L3 with positive refractive power has an object side surface S7 and an image side surface S8, and the image side surface S8 is convex.

The imaging lens system 200 provided in the second embodiment of the present invention satisfies the conditions of Table 2-1 and Table 2-2. The focal length f of the imaging lens system 200 is 0.4 mm, the total optical length is 4.96 mm, the aperture number F# is 1.63, and the field of view 2θ is 129.3°.

table 2-1

Table 2-2

In the above table, A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ , A ₁₄ , A ₁₆ refer to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders, respectively Aspheric coefficient.

In this embodiment, the on-axis point spherical aberration, lateral chromatic aberration, curvature of field and distortion are as shown in Figs. 6, 7 and 8a and 8b, respectively. Since the smaller the data range of the image point, the better the performance of the lens. It can be seen from Figure 6 to Figure 8b that the on-axis point spherical aberration, lateral chromatic aberration, curvature of field and distortion are all well corrected.

Example 3

Referring to FIG. 9, the imaging lens system 300 provided by the third embodiment of the present invention includes in turn from the object end to the image side end:

Flat glass G1, which has an object side surface S1 and an image side surface S2;

The first lens L1 with negative refractive power has an object side surface S3 and an image side surface S4, the object side surface S3 is a convex surface, and the image side surface S4 is a concave surface;

The second lens L2 has an object side surface S5 and an image side surface S6, the object side surface S5 is a convex surface, and the image side surface S6 is a concave surface;

Stop ST;

The third lens L3 with positive refractive power has an object side surface S7 and an image side surface S8, and the image side surface S8 is convex.

The imaging lens system 300 provided in the third embodiment of the present invention satisfies the conditions of Table 3-1 and Table 3-2. The focal length f of the imaging lens system 300 is 0.39 mm, the total optical length is 4.96 mm, the aperture number F# is 1.64, and the field angle 2θ is 129°.

Table 3-1

Table 3-2

In the above table, A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ , A ₁₄ , A ₁₆ refer to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders, respectively Aspheric coefficient.

In this embodiment, the on-axis point spherical aberration, lateral chromatic aberration, curvature of field, and distortion are shown in Figs. 10, 11, 12a, and 12b, respectively. Since the smaller the data range of the image point, the better the performance of the lens. As can be seen from Figure 10 to Figure 12b, the on-axis point spherical aberration, lateral chromatic aberration, field curvature and distortion are all well corrected.

Example 4

Referring to FIG. 13, the imaging lens system 400 provided by the fourth embodiment of the present invention includes in turn from the object end to the image side end:

Flat glass G1, which has an object side surface S1 and an image side surface S2;

The first lens L1 with negative refractive power has an object side surface S3 and an image side surface S4, the object side surface S3 is a convex surface, and the image side surface S4 is a concave surface;

The second lens L2 has an object side surface S5 and an image side surface S6, the object side surface S5 is a convex surface, and the image side surface S6 is a concave surface;

Stop ST;

The third lens L3 with positive refractive power has an object side surface S7 and an image side surface S8, and the image side surface S8 is convex.

The imaging lens system 400 provided in the fourth embodiment of the present invention satisfies the conditions of Table 4-1 and Table 4-2. The focal length f of the imaging lens system 400 is 0.46 mm, the total optical length is 5 mm, the aperture number F# is 1.63, and the field angle 2θ is 117.4°.

Table 4-1

Table 4-2

In the above table, A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ , A ₁₄ , A ₁₆ refer to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders, respectively Aspheric coefficient.

In this embodiment, the on-axis point spherical aberration, lateral chromatic aberration, curvature of field, and distortion are shown in Figs. 14, 15 and 16a and 16b, respectively. Since the smaller the data range of the image point, the better the performance of the lens. It can be seen from Figure 14 to Figure 16b that the on-axis point spherical aberration, lateral chromatic aberration, field curvature and distortion are all well corrected.

Please refer to Table 5. Table 5 shows the above four embodiments and their corresponding optical characteristics, including focal length f, total optical length, aperture number F#, and field angle 2θ.

table 5

Conditional	Example 1	Example 2	Example 3	Example 4
Focal length f(mm)	0.39	0.4	0.39	0.46
Optical length (mm)	5.0	4.96	4.96	5
Aperture F#	1.6	1.63	1.64	1.63
Field of view 2θ(°)	132	129.3	129	117.4

According to the above results, it can be seen that the total optical length of the imaging lens system of each embodiment does not exceed 5 mm, which effectively reduces the total optical length and is beneficial to the miniaturization of the lens.

In summary, in the imaging lens system provided by the present invention, the first lens has negative refractive power, its object-side surface is convex, its image-side surface is concave, the object-side surface of the second lens is convex, and the image-side surface is concave , The third lens has a positive refractive power, its image side surface is convex, and the diaphragm is located between the second lens and the third lens. The effective focal length f of the imaging lens system and the entrance pupil diameter EPD satisfy: f/EPD≤1.6, By reasonably matching and limiting each lens and diaphragm, the total optical length of the imaging lens system is shorter, which is beneficial to the miniaturization of the lens.

The above-mentioned embodiments only express several embodiments of the present invention, and the descriptions are relatively specific and detailed, but they should not be interpreted as limiting the scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (7)

1. An imaging lens system, characterized in that, from the object end to the image side end, it includes:

   plate glass;

   For the first lens with negative refractive power, the object side surface is convex, and the image side surface is concave;

   For the second lens with positive refractive power, its object-side surface is convex, and its image-side surface is concave;

   Aperture

   The third lens with positive refractive power has a convex surface on the image side;

   The effective focal length f of the imaging lens system and the entrance pupil diameter EPD satisfy: f/EPD≤1.6;

   The number of lenses in the imaging lens system is three;

   The imaging lens system satisfies the conditional formula:

   0＜BFL/IH＜0.2;

   Wherein, BFL represents the distance from the highest point of the third lens to the image plane, and IH represents the maximum image height of the imaging lens system;

   The imaging lens system also satisfies the conditional formula:

   -0.73＜(CT3-CT1)/(ET1-ET3)＜-0.45;

   Wherein, CT3 represents the central thickness of the third lens, CT1 represents the central thickness of the first lens, ET3 represents the edge thickness of the third lens, and ET1 represents the edge thickness of the first lens.
2. The imaging lens system of claim 1, wherein the imaging lens system satisfies the conditional formula:

   0.17<(SAG12-SAG11)/CT1<0.43;

   Wherein, SAG12 represents the sagittal height of the image side surface of the first lens, SAG11 represents the sagittal height of the object side surface of the first lens, and CT1 represents the center thickness of the first lens.
3. The imaging lens system of claim 1, wherein the imaging lens system satisfies the conditional formula:

   1.36＜f3/f＜1.56;

   Wherein, f3 represents the effective focal length of the third lens, and f represents the effective focal length of the imaging lens system.
4. The imaging lens system of claim 1, wherein the imaging lens system satisfies the conditional formula:

   (ND3-ND2)/(VD3-VD2)<0;

   Wherein, ND3 represents the refractive index of the third lens, ND2 represents the refractive index of the second lens, VD3 represents the Abbe number of the third lens, and VD2 represents the Abbe number of the second lens.
5. The imaging lens system of claim 1, wherein the imaging lens system satisfies the conditional formula:

   0.3<f3/f2<0.4;

   Wherein, f3 represents the effective focal length of the third lens, and f2 represents the effective focal length of the second lens.
6. The imaging lens system of claim 1, wherein the imaging lens system satisfies the conditional formula:

   -2＜(R32-R31)/(R32+R31)＜-1.3;

   Wherein, R32 represents the radius of curvature of the image side surface of the third lens, and R31 represents the radius of curvature of the object side surface of the third lens.
7. The imaging lens system of claim 1, wherein the surface shape of the aspheric surface of the imaging lens system satisfies the following conditional formula:

   

   Among them, z represents the distance of the surface from the surface vertex in the optical axis direction, c represents the curvature of the surface vertex, k represents the quadric surface coefficient, h represents the distance from the optical axis to the surface, B, C, D, E, F, G, H represents the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order surface coefficients respectively.

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